The present invention relates to a portable information apparatus, such as a portable computer, which has circuit components generating heat while operating, and more particularly to a structure which promotes heat radiation from the circuit components.
Recently book-size and notebook-size portable computers have had their performance greatly improved. There is the tendency that CPUs for use in portable computers are designed to operate at a higher and higher speed. A CPU of this type is provided in the form of a packaged module generally known as "CPU module." The CPU module is mounted on the circuit board incorporated in a computer housing.
The higher the speed with which a CPU processes data, the greater the electric power the CPU consumes. The greater the power it consumes, the more heat the CPU generates. It is necessary to enhance the efficiency of radiating heat from the CPU provided in the computer housing.
A known as a method of promoting heat radiation from a CPU is to attach a heat sink to the circuit board on which the CPU is mounted. The heat sink has a heat-radiating panel which receives the heat the CPU generates. The panel has a number of heat-radiating fins. The panel is contained in the computer housing and positioned almost parallel to the circuit board. In the computer housing, the panel performs natural radiation of the heat transmitted from the CPU to the heat sink.
A computer incorporating a CPU which generates a large amount of heat has an electric fan. The electric fan is located near the heat sink. The fan is started when the temperature ambient to the CPU reaches a predetermined value. While operated, the fan applies cooling air to the heat sink. The cooling air flows along the heat sink and out of the computer housing. The flow of cooling air drives the heat transmitted from the CPU to the heat sink, out of the computer housing.
As indicated above, the heat sink is provided within the computer housing. Hence, the size and shape of the heat-radiating panel and the number of the heat-radiating fins are determined from the amount of heat the CPU generates while operating, in order to raise the efficiency of radiating heat from the CPU. In the case of an electric fan, the rate at which the fan applies the cooling air to the heat sink is increased to enhance the efficiency of radiating heat from the heat sink.
Portable computers recently developed have a housing reduced in size to meet the demand made in the market. There is the trend that the space available in the housing decreases. The space for accommodating the heat sink is inevitably limited. The designer finds it difficult to make the heat sink larger than the present size.
It is demanded that the CPU be improved in performance. Hence, the trend is that the CPU generates an increasing amount of heat while operating. It is now almost impossible for the heat sink to radiate the heat with a sufficient efficiency. The conventional method may fail to radiate the heat sufficiently if the heat the CPU generates increases further. There is a demand for a heat-radiating structure which can radiate the heat generated by the CPU, with a higher efficiency.
The CPU will generates less heat while operating only if its clock frequency is decreased. If the clock frequency of the CPU is lowered, however, the portable computer will have lower performance. This would run counter to the recent demand that the performance of portable computers be improved further.